1. Field of the Invention
The invention relates to an image processing apparatus and method and, more particularly, to an apparatus and method for encoding/decoding image data.
2. Related Background Art
In recent years, by the advancement of a digital signal processing technique, a large amount of digital information such as moving images, still images, audio sound, or the like is high efficient encoded and can be recorded to a small magnetic medium or can be transmitted to a communication medium. Various examinations have been made with respect to an apparatus for encoding various video signals having different aspect ratios of the picture plane into a signal train of a common format by applying such a technique.
For example, as shown in FIG. 1, there is considered an encoding apparatus such that a wide video signal having an aspect ratio of (9:16) of 360 pixels in the vertical direction and 720 pixels in the lateral direction is converted into a standard video signal having an aspect ratio of (3:4) of 480 pixels in the vertical direction and 720 pixels in the lateral direction, thereby commonly using an encoding circuit of the standard video signal.
FIG. 2 is a block diagram showing an example of a construction of a conventional encoding apparatus.
In FIG. 2, reference numeral 201 denotes an input terminal of a video signal; 202 and 204 frame buffers; 203 a vertical line filter; 205 a change-over switch; 206 a block forming circuit; 207 an orthogonal transform circuit; and 208 an output terminal.
The operation will now be described.
An input video signal which is supplied to the input terminal 201 is a wide video signal having an aspect ratio of (9:16) of 360xc3x97720 pixels shown in FIG. 3A or a standard video signal having an aspect ratio of (3:4) of 480xc3x97720 pixels shown in FIG. 3B and comprises scanning lines in the horizontal direction as shown in the diagrams. In this apparatus, therefore, the wide video signal of one picture plane is stored into the frame buffer 202 and is rearranged to a signal train in the vertical direction. A converting process in the vertical direction is performed by the vertical line filter 203.
The vertical line filter 203 is an interpolation filter for converting a wide video image into a standard video image and converts the video image from 360 pixels to 480 pixels. Since an output of the vertical line filter 203 has the pixel train in the vertical direction, it is again rearranged into the scanning lines in the horizonal direction by the frame buffer 204.
The change-over switch 205 selects either one of the signal trains which are supplied from the frame buffer 204 and input terminal 201 and supplies the selected signal train to the block forming circuit 206 in accordance with a selection signal. That is, when the signal that is supplied to the input terminal 201 is the wide video signal of 360xc3x97720 pixels, the signal train from the frame buffer 204 is selected. When the signal which is supplied to the input terminal 201 is the standard video signal of 480xc3x97720 pixels, the signal train applied to the input terminal 201 is selected.
The block forming circuit 206 divides the signal train supplied from the change-over switch 205 into blocks on a unit basis of 8 pixels (in the vertical direction)xc3x978 pixels (in the lateral direction). The (8xc3x978)-pixel blocks are 2-dimensional discrete cosine transformed by the orthogonal transform circuit 207 and are outputted from the output terminal 208.
In the encoding apparatus as mentioned above, in order to convert a resolution of the video image, storage elements of the frame units, such as frame buffers 202 and 204, are necessary, and undesirably increase the overall size of the apparatus. Further, it takes a long processing time for the converting process.
In consideration of the above background, it is an object of the present invention to provide an image processing apparatus and method which can encode/decode even various image data in which pixel constructions of one picture plane are different by using a common encoding circuit without enlarging a circuit scale and without substantially changing a conventional processing time.
According to one preferred embodiment of the invention, the above object is accomplished by an image processing apparatus/method, wherein a plurality of kinds of video signals in which aspect ratios of an image are different are selectively inputted and, by executing a predetermined arithmetic operation by using a predetermined coefficient selected in accordance with the kind of inputted video signal, the inputted video signal is orthogonally transformed.
According to another preferred embodiment, there is provided an image processing apparatus/method, wherein a video signal which was orthogonally transformed and encoded is inputted and the inputted video signal is inversely orthogonally transformed by executing a predetermined arithmetic operation by using a predetermined coefficient, and the inversely orthogonally transformed video signal is outputted. The arithmetic operating process selects the coefficient to be used for the predetermined arithmetic operation in accordance with the aspect ratio of the video signal.
According to still another preferred embodiment, there is provided an image processing apparatus/method, wherein (mxc3x97n) signals are collected from an input signal train and are divided into blocks, the signals of the divided blocks are converted into (ixc3x97j) signals of blocks, and the block converted signals are orthogonally transformed on a block unit basis.
According to further another preferred embodiment, there is provided an image processing apparatus/method, wherein an encoded signal obtained by encoding a signal divided into blocks by (mxc3x97n) signals is inversely orthogonally transformed on the block unit basis, the inversely orthogonally transformed signal is converted into (ixc3x97j) signals of blocks, and each of the block converted blocks is connected, thereby reconstructing a video signal.
Other objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.